From U.S. Pat. No. 5,211,407 a fastening of rotor blades of a compressor on the disk of the compressor rotor is known, in which the locking of the rotor blades against axial displacement is effected by an annular retaining segment. For this, the disk has radially inwards extending hooks on the end face between two rotor blade retaining slots into which is hooked a retaining segment. The retaining segment forms a stop for the rotor blade held in the retaining slot and so locks this against axial displacement.
In addition to this, a method for the fitting of rotor blades in a disk is described in DE 26 06 565. In this, the end face regions of a platform of a rotor blade are deformed in such a way that after a caulking action the material regions of the platform which are facing the outer periphery of the disk bear tightly against the disk in order to achieve a frictional damping.
Furthermore, CH 489 698 A shows a device for the locking of rotor blades of turbines individually positively retained in axial slots. A T-form slot with undercuts is located on the end face of a shaft collar in such a way that the undercut intersects from the bottom the slot base of the retaining slots of the rotor blades. For the axial locking of the rotor blades a locking element is insertable in the T-form slot after the fitting of the rotor blades, which engages in a recess correspondingly formed in the blade root.
In addition, it is known that rotor blade roots of rotor blades of a compressor are locked against axial displacement by plastic deforming.
FIG. 7 shows for this a cut-out of a compressor disk 19 as claimed in the prior art. For the holding of rotor blades, retaining slots 21 are provided in the outer periphery 23 of the compressor disk 19. In addition, recesses 29 are located on the two end faces 25 of the compressor disk 23, which in each case merge into the slot base 27 of the radially outer-lying retaining slot 21.
FIG. 8 shows the cross section through a compressor disk 19 according to FIG. 7 along the section VIII-VIII. The recess 29 is constructed as a chamfer 30 with an angle of 45°.
After the introducing of a rotor blade 16, material of the rotor blade root 33 is plastically deformed into the region of the chamfer 30 on both sides by a caulking action. The projection formed in this way on the rotor blade root 33 then locks the rotor blade 16 against axial displacement, while the projection bears against the chamfer 30 which is inclined by 45° to the displacement direction.
As, however, during the caulking action the projection on its side facing the chamfer assumes a rounded form, the latter bears only partially on the chamfer which can lead to a smaller retaining force.
During the starting of the cold compressor and after the shutting down of the hot compressor, axially orientated stresses can arise in the rotor blade fastening owing to different thermal expansions of rotor blade and disk, which with repeated occurrence can deform the projection. This effect, also known as “Blade Walk”, can lead to the axial play of the compressor rotor blades and this to flow losses in the compressor.